The invention relates to an occluder for sealing body orifices of the human or animal body, in particular an occluder for percutaneous transcatheter sealing of atrial septal defects of the human or animal heart.
The foramen ovale is an orifice in the septum between left and right heart atrium in the foetus and the newborn. As a general rule the gap closes over in the first few months of life. In some 20% of humans however this closure is incomplete, leaving a small orifice. This persistent foramen ovale has no effects on the state of health and is accordingly not noticeable to the person concerned. Under certain circumstances it does foster the advent of an apoplectic stroke. Because the open foramen enables blood to shift from the right to the left atrium it can eventuate that a blood clot washed out of a leg vein thrombosis directly enters the arterial circulation via the left atrium and thus possibly reaches the brain. Normally, it would be first sent from the right heart compartment to the pulmonary circulation and filtered out in the lung.
For sealing off septum or vessel defects occluders are used which can be positioned and activated with a catheter. An occluder of the abovedescribed type is known for example from EP-B1-0 959 777. The purpose of occluders is e.g. to seal a persistent foramen ovale (PFO) or an atrium septum defect, for example of secundum type (ASD II [atrial septal defect]). Implanting proceeds as follows. The operator pushes a catheter in from the groin through the vena cava inferior into the right heart atrium and from there through the open foramen ovale into the left atrium. Occluders from the prior art are known, which are folded up like a double umbrella and can be transported by the catheter. A shield-like closure body of the occluder is opened at the target site in the left atrium. The catheter is then withdrawn into the right atrium and a second shield-like sealing body of the occluder is opened. As a result, the occluder lies on both sides of the atrium septum. After becoming overgrown by the inner skin of the heart the foramen ovale is permanently sealed.
With the previously described implant process intervention under X-ray vision and in parallel to this transoesophageal echocardiography (TEE) take place: A sound head placed in the oesophagus generates images of the adjacent heart. At the same time the operator is presented with magnetic resonance (MR) images produced prior to the procedure. MR monitoring of the implanting of an occluder is only very limited or not even possible. The occluder gives rise to image artefacts, whereby these are in particular susceptibility artefacts and so-called RF artefacts (radiofrequency artefacts). Susceptibility artefacts are attributable to the fact that the occluder has greater susceptibility than human tissue. RF artefacts are created by RF excitation pulses. In the process electric currents are induced by the time-variable magnetic field components of the RF pulses in the occluder. These artefacts are gaining significance in particular with occluder materials such as nitinol or tantalum. As a result, an X-ray process for image display during implanting of the occluder cannot be omitted, with the known drawbacks to such methods.